1. Field of the Invention
The present invention relates to a liquid absorbent which is used under dripping foods as a food drip-absorbing sheet, and is also usable in sanitary napkins or pantiliners.
2. Description of the Related Art
When retailed in the stores or the like, perishable foods, especially seafood and meat are laid on trays, and then the trays and perishable foods laid on the trays are individually covered with a wrapping film.
While laid on trays, juices or other liquids (these are referred to as xe2x80x9cdripsxe2x80x9d hereinafter) exude from the foods such as seafood and meat therein. If such drips accumulate in trays, the appearances of the foods in showcases tend to be degraded. In addition, if the drips are kept in long contact with such perishable food, this provides an environment supportive of the growth of bacteria. Especially for meat, if the interface between meat and trays is not aerated, the surface of the meat airtightly kept in contact with the trays will be browned due to discoloration. Accordingly, breathable, liquid absorbent capable of absorbing drips of foods is disposed between trays and foods.
As a liquid absorbent of this type, a liquid absorbent comprising a liquid-absorbing layer of fibers and a liquid-pervious synthetic resin film bonded to the surface of the liquid-absorbing layer is well known in the art. For bonding the liquid-absorbing layer and the synthetic resin film, for example, a resin adhesive is used in Japanese Unexamined Patent Publication (Kokai) No. Heisei 7-241944. Further, in Japanese Examined Patent Publication (Kokoku) No. Heisei 4-70983, a synthetic resin film combined with a liquid-absorbing layer is perforated with hot needles to melt around the perforations formed through the film, and the film is thus adhered to the liquid-absorbing layer via the melted resin around the perforations. Still further, in Japanese Unexamined Patent Publication (Kokai) No. Heisei 9-86569, a mesh film of synthetic resin is heat sealed with a liquid-absorbing layer.
The conventional liquid absorbents set forth above, however, possess certain disadvantages. Specifically, as disclosed in Japanese Unexamined Patent Publication (Kokai) No. Heisei 7-241944, the liquid absorbent that comprises a synthetic resin film and a liquid-absorbing layer bonded via a resin adhesive therebetween requires the process of adhesive application, thereby increasing the production costs thereof. In addition, in this, if the amount of the adhesive used therein is too much, the excessive adhesive will penetrate into the liquid-absorbing layer and will retard liquid diffusion in the layer. On the other hand, if the amount of the adhesive used therein is too small, the synthetic resin film and the liquid-absorbing layer could not be sufficiently bonded in the interface therebetween and tend to form a gap therein. The gap, if formed, retards liquid diffusion in the interface between the synthetic resin film and the liquid-absorbing layer. If the liquid diffusion in the interface between them is retarded, it interferes with the liquid absorption of the entire liquid-absorbing layer, and, as a result, the drips of food tend to remain on the surface of the resin film.
Further, Japanese Examined Patent Publication (Kokoku) No. Heisei 4-70983 in which a synthetic resin film is adhered to the liquid-absorbing layer via the melted resin around the perforations formed in the resin film, is problematic in that the bonding strength between the synthetic resin film and the liquid-absorbing layer greatly varies, and, in addition, a gap is formed in the interface between the synthetic resin film and the liquid-absorbing layer to retard liquid diffusion in the interface between them.
Still further, Japanese Unexamined Patent Publication (Kokai) No. Heisei 9-86569 in which a mesh or film of synthetic resin is heat-sealed with a liquid-absorbing layer, is also problematic in that the liquid-absorbing layer is compressed by application of heat and pressure for heat-sealing the two, whereby the liquid-absorbing layer is crushed to lose bulkiness and the liquid absorption thereof is lowered. In addition, heat-sealing could not produce sufficient adhesion in the interface between the synthetic resin mesh or film and the liquid-absorbing layer, so that there is a limit to promote the liquid diffusion in the interface.
The present invention has been worked out in view of the shortcoming in the prior art set forth above. It is therefore an object of the present invention to provide a liquid absorbent comprising a liquid-absorbing layer and a synthetic resin film, in which the liquid-absorbing layer and the synthetic resin film can be firmly bonded in the interface therebetween without significantly lowering the bulkiness of the liquid-absorbing layer, and therefore the liquid diffusion in the interface can be promoted to rapidly lead the liquid applied to the surface of the synthetic resin film into the liquid-absorbing layer.
According to an aspect of the invention, a liquid absorbent comprising:
a liquid-absorbing layer of synthetic fibers by hydrophilic treatment and/or hydrophilic fibers, and a synthetic resin film bonded to a surface of the liquid-absorbing layer and having a large number of through-holes,
wherein the synthetic resin film is laminated on the surface of the liquid-absorbing layer through melt extrusion thereon, and the liquid-absorbing layer and the synthetic resin film are airtightly bonded to each other.
Preferably, a portion of the resin constituting the synthetic resin film penetrates into the liquid-absorbing layer in the boundary between the liquid-absorbing layer and the synthetic resin film.
In the step of melt-extrusion lamination, when the synthetic resin film is laminated on the liquid-absorbing layer, the synthetic resin film and the liquid-absorbing layer firmly bond to each other via the interface between them, thereby increasing the density of the fibers and the resin in that interface and promoting liquid diffusion therein. Accordingly, the liquid applied to the surface of the synthetic resin film is rapidly led into the liquid-absorbing layer through the through-holes (or perforations) formed in the resin film.
Preferably, the synthetic resin film is composed of a first layer formed through melt-extrusion lamination on the surface of the liquid-absorbing layer, and a second layer formed through melt-extrusion lamination on a surface of the first layer.
In this case, it is desirable that the thickness of the second layer is larger than that of the first layer, for example, the thickness of the first layer falls between 1 xcexcm and 30 xcexcm and that of the second layer falls between 5 xcexcm and 50 xcexcm, and that the overall thickness of the synthetic resin film is at least 6 xcexcm, more preferably at least 10 xcexcm.
Also preferably, the density in the boundary between the liquid-absorbing layer and the synthetic resin film is higher than that in any other region of the liquid-absorbing layer.
When the synthetic resin film has a multi-layered structure, it is possible to avoid lowering the bulkiness of the underlying liquid-absorbing layer in the step of melt-extrusion lamination.